The main objective of this research is to establish uterine peroxidase as a marker protein which can be used to study the molecular mechanism(s) of estrogen action in mammalian tissue of the reproductive tract. This marker will then be used to study several aspects of estrogen regulation of gene function. The uterine peroxidase will be assayed both biochemically and histochemically to study specific cell responses. This enzyme will be used to study hormone interactions involved in the regulation of estrogen-induced gene expression. The main interacting hormones to be studied are the progestins and the thyroid hormones. Finally the peroxidase will be used to examine the ontogeny of estrogen responsiveness. In order to establish estrogen-induced uterine peroxidase as a marker protein, de novo synthesis must be demonstrated. In order to show de novo synthesis, it is necessary to purify the enzyme and raise an antibody which is specific for the uterine peroxidase. The availability of an antibody will allow for the isolation and cell-free translation of peroxidase mRNA. With this capability, it is then possible to study changes in peroxidase activity and peroxidase mRNA levels due to estrogen and the modulation of these changes by other hormones such as progesterone, the aim being to establish at least at what point do these hormones regulate estrogen action, pre- or post-receptor levels, transcription or translation or post-translation? Measurements of receptor, peroxidase mRNA and peroxidase activity will enable us to answer some of these questions. Using a specific marker, it will be possible to quantitatively correlate nuclear binding in terms of nuclear receptor and possible nuclear acceptor sites with a quantitative response. Peroxidase activity and mRNA will be determined in neonates of various ages, and the responsiveness will be studied in terms of nuclear uptake, type of receptor, nucleosome binding and changes in non-histone and histone proteins.